this is something i've been thinking about a lot recently so maybe i'm way off with my thoughts on it..

if CO is solid then his range will be pretty wide. similarly if he folds more than 70% of the time then 3betting him HU is probably going to be +EV. the problem is if he is folding lots to 3bets and you 3bet a hand like AQ, then you kind of waste the hand because you will dominate some of his Qx and Ax hands when you call and play postflop. also if they are either 4betting or folding then AQ is nothing but a bluff 3bet. im not entirely sure about this though because then we are playing OOP without initiative and it could cost money.

if CO doesn't fold to 3bets and prefers to call, then he will have a much wider 3bet-calling range - maybe even something similar to his open raising range and so it will all of a sudden be profitable to 3bet AQ type hands for value against him because he isn't folding but calling with his wide range.

if SB is a fish and CO is a solid player i would be tempted to squeeze maybe A9+ here for value - assuming CO will fold and we get to play IP against the fish. Also, the fish might fold sometimes and we profit with our hand. if CO 4bets then we have an easy fold and if he calls then we will most likely shut down on the flop because we will be OOP against a solid player and a fish - we have no FE.

i guess it all comes down to how people react to 3bets and with what range. im currently working on this myself so as i say, this is just my thoughts on it and i might not be right.

Next, it's quite dependent on opponents. Overall, Axo plays badly multiway and even HU vs a call OOP so I suggest 3betting AT+ and just mucking worse. You can use some good suited Kx and Qx hands to squeeze instead of offsuit Ax.

If you always have these stack sizes, forget about polarized 3betting range and depolarize. CO will never fold a hand having position on 2 players, one against which he is 200bb deep.

100bb deep you should basically try and squeeze CO out with all hands that don't get you more value 3way. For me, it's almost all hands I want to play, but that's just because I want to be alone with the SB (whether fish or reg, once he flats CO open he has a face-up super capped mediocre strength range OOP vs me, easy money) and possibly annoy CO that he cannot play position and make him spew at some point. It's simply creating a very aggressive image in a simple spot that will pay off later.